Stent lining

ABSTRACT

The invention features a catheter assembly and methods for delivering a hydrogel-lined stent to a body lumen, and methods for lining a stent with a hydrogel. The assembly includes a catheter which has a balloon at least a portion of which is coated with a hydrogel and an expansible stent mounted on the balloon in a contracted condition for passage with the catheter to a site of a body. Expansion of the balloon lodges the stent in the body with hydrogel coated on the inner surfaces of the stent as a lining.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation-in-part of application U.S.Ser. No. 08/097,248, filed Jul. 23, 1993, which is acontinuation-in-part of application U.S. Ser. No. 07/795,976, filed Nov.22, 1991, issued as U.S. Pat. No. 5,304,121, which is acontinuation-in-part of application U.S. Ser. No. 07/635,732, filed Dec.28, 1990, now abandoned. This application is also a continuation-in-partof application U.S. Ser. No. 08/507,844, filed Jul. 27, 1995, which is acontinuation-in-part of U.S. Ser. No. 07/268,999, filed Jun. 30, 1994,issued as U.S. Pat. No. 5,439,446. The entire contents of each of theseapplications is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

[0002] The invention relates to the lining of bodily stents.

[0003] Angioplasty, which involves the insertion of a catheter, e.g., aballoon catheter, into a blood vessel to expand an occluded region ofthe blood vessel, is frequently used to treat arteriosclerosis.Restenosis, or closing of the vessel, is a process that may occurfollowing angioplasty. This process may be characterized by theproliferation of smooth muscle cells stimulated by the angioplastytreatment. Restenosis may also occur as a result of clot formationfollowing angioplasty, due to injury to the vessel wall which triggersthe natural clot-forming cascade of the blood.

[0004] A number of different approaches have been taken to preventpost-angioplasty vessel reclosure. One such approach has been theplacement of a medical prosthesis, e.g., an intravascular metal stent,to mechanically keep the lumen open. For example, an intravascular stentmade of an expandable stainless steel wire mesh tube has been used toprevent post angioplasty restenosis and vessel reclosure. The stent maybe formed of wire configured into a tube and is usually delivered intothe body lumen using a catheter. The catheter carries the prosthesis ina reduced-size form to the desired site. When the desired location isreached, the prothesis is released from the catheter and expanded sothat it engages the lumen wall. Stents are typically fabricated frommetals, alloys, or plastics and remain in the blood vessel indefinitely.

SUMMARY OF THE INVENTION

[0005] The invention features a catheter assembly for delivering a stentto a body lumen and lining the stent with a hydrogel to reduce shearforces and flow disturbances in the blood, protect damaged cellsadjacent to the stent, reduce platelet deposition at the stent site,and/or deliver a drug to reduce or prevent restenosis of stented lumens.The assembly includes a catheter which has a balloon at least a portionof which is coated with a hydrogel. The assembly also includes anexpansible stent mounted on the balloon in a contracted condition forpassage with the catheter to a site of a body lumen. Expansion of theballoon lodges the stent in the body lumen with the hydrogel depositedon an inner surface of the stent as a lining. The hydrogel may becrosslinked to form a relatively permanent lining on the inner surfacesof the stent or left uncrosslinked to form a relatively degradablelining on the inner surfaces of the stent. Preferably, the longevity ofa crosslinked form of a given hydrogel as a stent lining is at leasttwice that of its uncrosslinked form.

[0006] The hydrogel is selected from the group consisting of a polyacid,e.g., a poly(acrylic acid) or a polycarboxylic acid, cellulosic polymer,collagen, gelatin, albumin, alginate, poly 2-hydroxy ethyl methylacrylate (HEMA), polyvinylpyrrolidone, maleic anhydride polymer,polyamide, polyacrylamide, polyvinyl alcohol, polyethylene glycol,polyethylene oxide, and polysaccharide, e.g., a mucopolysaccharide suchas hyaluronic acid. For example, the hydrogel may be a poly(acrylicacid), e.g., CARBOPOL® 941 poly (acrylic acid) (BF Goodrich), in acrosslinked or uncrosslinked form.

[0007] In some cases, the hydrogel may be crosslinked prior to liningthe stent. For example, the hydrogel coating on a balloon may becontacted with a primer dip before the hydrogel is deposited onto theinner surfaces of a stent. Alternatively, the hydrogel lining may becontacted with a crosslinking agent in situ, i.e., the balloon portionof the catheter with a coating of uncrosslinked hydrogel is insertedinto the body and after the deployment of the stent in the body lumenand deposition of the hydrogel onto the inner surfaces of the stent, thehydrogel is contacted with a crosslinking agent.

[0008] The hydrogel may include a therapeutic agent, e.g., a drug, toreduce or prevent clotting and/or restenosis at the stent site. Forexample, the therapeutic agent may reduce or eliminate acute thrombosisof the stent and reduce in-stent restenosis or interfere with cellmetabolism (e.g., an anti-metabolite), thereby killing undesired cells.The therapeutic agent may be an anti-platelet drug, anticoagulant drug,anti-metabolite drug, anti-angiogenic drug, or anti-proliferative drug.The therapeutic agent may be an anti-thrombogenic agent such as heparin,PPACK, enoxaprin, aspirin, and hirudin or a thrombolytic agent such asurokinase, streptokinase, and tissue plasminogen activator. The hydrogelmay also include an agent which inhibits platelet deposition or smoothmuscle cell proliferation. The agent may also be a nucleic acid whichencodes a therapeutic protein, e.g., a naked nucleic acid or a nucleicacid incorporated into a viral vector-or liposome. By naked nucleic acidis meant an uncoated single or double stranded DNA or RNA molecule notincorporated into a virus or liposome. Antisense oligonucleotides whichspecifically bind to complementary mRNA molecules and thereby reduce orinhibit protein expression can also be delivered to the stent site viathe hydrogel coating on the balloon catheter. The drug may beincorporated into microspheres to prolong the time over which adelivered drug is released and minimize spreading of the delivered drugto non-target sites.

[0009] Rather than administering the hydrogel lining via a coating on aballoon, the catheter may include a delivery port for administering ahydrogel to the inner surfaces of the stent. For example, the balloonmay include a first layer and a second outer aperatured layer overlyingthe delivery port. The hydrogel is administered through the outeraperatured layer of the balloon to contact the inner surfaces of thestent to create a lining therein. After the hydrogel is applied to thestent, a crosslinking agent may be administered to contact the hydrogel.For example, an aginate hydrogel can be crosslinked by contacting itwith calcium gluconate, and a hyaluronic acid hydrogel can becrosslinked by contacting it with divinyl glycol.

[0010] Lining a stent using a porous balloon, e.g., a channeled balloon,is accomplished by deploying the stent positioned over the porousballoon and then infusing a hydrogel through the pores in the balloon toline the inner surfaces of the stent with a polymeric layer tofacilitate smooth flow of blood through the stent. The hydrogel fillsthe interstices of a mesh stent creating a smooth lining inside thestent.

[0011] Alternatively, one or more delivery ports may be located proximalto the balloon over which the stent is mounted, i.e., upstream of thestent with respect to the blood flow, and the hydrogel administered viathe delivery port and carried to the inner surfaces of the stent by theblood flow.

[0012] The invention also features a method for lining a stent whichincludes the steps of providing a catheter assembly including a balloonat least a portion of which is coated with a hydrogel over which ismounted an expansible stent in a contracted condition, introducing theassembly into a body lumen, and inflating-the balloon to lodge the stentin the body lumen and to release the hydrogel from the coated portion ofthe balloon to the inner surfaces of the stent to create a lining.Preferably, the body lumen is a blood vessel, more preferably it is anartery, such as an artery occluded by an arteriosclerotic plaque.

[0013] Also within the invention is a method of lining a stent which hasbeen previously deployed in a body lumen of a patient. The methodincludes the steps of providing a catheter including a balloon at leasta portion of which is coated with a hydrogel, introducing the catheterinto the body lumen, advancing the catheter in the body lumen until theballoon is positioned proximate to the inner surfaces of the stent, andinflating the balloon to release the hydrogel from the coated portion ofthe balloon to the inner surfaces of the stent to create a lining. Thecatheter may include a sheath over the hydrogel-coated portion of theballoon which is removed prior to inflating the balloon.

[0014] A previously-deployed stent may also be lined using a catheterwhich includes a balloon and delivery port, the balloon portion of whichcontains a first layer and a second outer aperatured layer overlying thedelivery port. The method includes the steps of introducing the catheterinto the body lumen, advancing the catheter in the body lumen until theouter aperatured layer is positioned proximate to the inner surfaces ofthe stent, delivering a hydrogel into a space between the first layerand the second outer aperatured layer, and inflating the balloon topress the hydrogel through the outer aperatured layer thereby depositingthe hydrogel on the inner surfaces of the stent as a lining.

[0015] A previously-deployed permeable stent, e.g., an open mesh metalstent, in the region of a blood vessel affected by an aneurism may beselectively lined with a hydrogel to render the portion of the stentproximate to the aneurism impermeable, thereby preventing blood flowinto the aneurism. By “selectively lining” is meant depositing a liningmaterial, e.g., a hydrogel, in a desired region of the inner surface ofa stent while leaving other regions of the inner surface of the stentfree from the lining material. The hydrogel lining is delivered to thestent as a coating on a balloon portion of a catheter or via ports of achanneled balloon. For example, a method of selectively lining apermeable stent to treat an aneurism, includes the steps of providing aballoon catheter with at least a portion of the balloon coated with ahydrogel; introducing the catheter into an aneurismal blood vessel inwhich a permeable stent has previously been deployed in the region ofthe aneurism; advancing the catheter in the affected vessel until thecoated portion is positioned proximate to the aneurism; and inflatingthe balloon to release the hydrogel from the coated portion to an innersurface of the stent proximate to the aneurism. The hydrogel liningrenders the inner surface of the stent near the aneurism impermeable,thereby reducing or preventing blood flow into the aneurism, butpermitting blood flow through the unlined portions of the stent to orfrom branching blood vessels in an area of the vessel unaffected by theaneurism.

[0016] Other features and advantages of the invention will be apparentfrom the following description of the preferred embodiments thereof, andfrom the claims.

BRIEF DESCRIPTION OF THE DRAWING

[0017]FIG. 1 is a cross-sectional view of a hydrogelcoated ballooncatheter with a stent mounted on the balloon portion of a catheter inthe region of a thrombus before radial expansion of the balloon sectionand stent.

[0018]FIG. 2 is a cross-sectional view of a stent compressed against awall of a body lumen by radial expansion of the balloon portion of thecatheter and release of the hydrogel from the balloon portion of thecatheter onto the inner surfaces of the stent.

[0019]FIG. 3 is a cross-sectional view of a hydrogel-lined stentpositioned inside the compressed thrombus as the catheter is removed.

[0020]FIG. 4 is a cross-sectional view of a stent previously-deployed ina body lumen and a hydrogel-coated catheter prior to expansion of theballoon portion to release the hydrogel onto the inner surfaces of thepreviously-deployed stent.

[0021]FIG. 5 is a photograph of a model body lumen in which an open meshmetal stent has been deployed.

[0022]FIG. 6 is a photograph of a model body lumen in which apreviously-deployed open mesh metal stent has been lined with a hydrogelusing a hydrogel-coated balloon catheter.

DETAILED DESCRIPTION

[0023] The inner surfaces of a stent may be lined with a hydrogelpost-deployment or simultaneously with deployment of the stent into abody lumen. The hydrogel is delivered as a coating on a balloondilatation catheter. The hydrogel is released from the balloon onto thestent by expanding the balloon into the stent forcing the hydrogel ontothe inner surface of the stent.

[0024] The hydrogel which has been deposited onto the stent provides asmooth surface lining to protect cells of the lumen, e.g., a bloodvessel wall, which may have been damaged during deployment of the stent,e.g., when the stent is lodged into the vessel wall. The stent liningalso reduces flow disturbances, e.g., turbulence, and shear in thebloodstream in the area of a-blood vessel in which the stent is lodged.The stent lining may also reduce or prevent blood flow through aparticular lined region of a stent, e.g., in the region of an aneurism.

[0025] Stents may be lined with a hydrogel in the absence of drug or inthe presence of drug. In addition to the mechanical advantages describedabove, the addition of drugs into the hydrogel provides furthertherapeutic benefits. For example, a hydrogel lining which containsalbumin reduces platelet deposition at the stent site. Other drugs,e.g., agents which reduce the proliferation of smooth muscle cells, canalso be incorporated into the hydrogel stent lining to reduce intimalsmooth muscle cell proliferation which may contribute to restenosis atthe stent site. The stent lining may also be used to deliver a drug,e.g., heparin, to enhance antithrombogenicity.

[0026] Preparation of a Hydrogel-Coated Angioplasty Balloon

[0027] A hydrogel coating on an angioplasty balloon was formed asfollows. The surface of the balloon (polyethylene) of an angioplastycatheter was prepared by wiping down the catheter with clean cloth. Theballoon typically has an outer diameter (O.D) of about 3.5 mm(inflated). The balloon was dipped in a 10% solution of CARBOPOL® 941poly(acrylic acid) having a molecular weight of about 1,200,000 Daltonsin dimethylformamide (DMF) and tertiarybutyl alcohol. After drying atabout 85° C. for 30 minutes, a smooth coating was obtained. The balloonwas then oven-dried for 8 hours at 50° C.

[0028] Alternatively, the poly(acrylic acid) coating may be crosslinkedby dipping the poly(acrylic acid)-coated balloon into a primer dip of4,4′ diphenylmethane diisocyanate (MDI) in methylketone for 30 min. anddrying in an air oven at 85° C. for 30 min.

[0029] One function of the drying steps is to remove solvent from thecoating. The surface of the balloon becomes instantly lubricious uponexposure to water. The poly(acrylic acid) is typically at aconcentration of about 0.1 to 50% by weight. The formation of thehydrogel is further described in U.S. Pat. No. 5,091,205, herebyincorporated by reference.

[0030] Other hydrogel polymers, such as collagen, albumin, derivitizedalbumin, gelatin, polyvinyl alcohol (PVA), cellulosics, alginates,acrylics, HEMA, polyethylene glycols, polyethylene oxides, polyacids,polyanhydrides, and polyacrylamides can be used to coat the balloon.Like the poly(acrylic acid) polymer coating, these hydrogel polymers arereleased from the balloon onto the inner surfaces of a stent bycompression of the coated balloon against the stent. The hydrogelpolymers used are swellable but not dissolvable. As a result, a sheathover the hydrogel-coated balloon is not required to prevent loss of thehydrogel coating prior to release onto the inner surfaces of the stent.However, a sheath may be used in any of the embodiments discussed hereinto facilitate placement of the catheter and/or deployment of thecatheter or stent. For simultaneous stent deployment and lining, anexpansible stent in a contracted form is placed over the hydrogel-coatedballoon portion of the catheter prior to introduction of thecatheter/stent assembly into the body A drug such as ananti-thrombogenic agent may be applied to the coating or incorporatedinto the coating. For example, a solution of 10,000 units sodium heparin(Fisher Scientific, Pittsburgh, PA; USP Grade; 1000 units/ml which isthen added to 650 cc distilled water) may be applied to the hydrogelcoating by dipping the coated catheter into the heparin solution forabout 1 minute at room temperature.

[0031] The heparin does not form a complex with the hydrogel solutionand is therefore freely released in response to compression of thehydrogel. A drug may be formulated to be rapidly released uponcompression of the hydrogel, e.g., upon release of the hydrogel from theballoon to the inner surfaces of the stent, or to be slowly releasedover time, e.g., by diffusion from the hydrogel stent lining.Alternatively, the drug, e.g., urokinase, may form a complex with thehydrogel, or the drug releasing system may be the hydrogel itself, e.g.,nitrosylated albumin which releases nitric oxide.

[0032] After a catheter is prepared for use as discussed above, thecatheter may be introduced into the patient using known methods. Theballoon is then expanded at a desired location to deploy the stent andsimultaneously release the hydrogel from the balloon to line the stent.The hydrogel is deposited and remains on the stent as a lining after theballoon is deflated. The hydrogel coating can also be applied to apre-existing stent, e.g., one that has already been expanded and/ordeployed in a body lumen, of a patient. Lining a previously-deployedstent is accomplished by introducing the hydrogel-coated ballooncatheter into the vessel, positioning the balloon portion adjacent tothe previously-deployed stent, and inflating the balloon portion againstthe inner surfaces of the previously-deployed expanded stent to releasethe hydrogel thereby lining the stent.

EXAMPLE 1 Lining of an Intravascular Stent with a HydrogelSimultaneously with Deployment of the Stent into a Body

[0033] As shown in FIG. 1, a stent 50 is placed over the ballooncatheter 51 which is coated with a hydrogel coating 52 in the presenceor absence of a drug. The balloon 51 and stent 50 are advanced untilthey-reach the region of the occlusion 53 in the vessel 54. After theballoon 51 and stent 50 have been positioned inside the vessel 54, thestent 50 is radially expanded and the hydrogel coating 52 released fromthe balloon 51 onto an inner surface of the stent 50 by the admission ofpressure to the balloon 51. As a result, the stent is compressed againstthe vessel wall 54 with the result that occlusion 53 is compressed, andthe vessel wall 54 surrounding it undergoes a radial expansion. Thepressure from inflating the balloon also releases the hydrogel coating52 onto the inner surface of the stent 50, thus lining it. The stent 50is held in position in the expanded state as shown in FIG. 2. Thepressure is then released from the balloon and the catheter is withdrawnfrom the vessel, leaving the hydrogel as a lining of the deployed stent,as shown in FIG. 3.

[0034] In the embodiments in which the hydrogel stent lining contains adrug, the hydrogel and drug may be selected such that an initial highdosage of drug is delivered to adjacent tissue upon initial compressionof the hydrogel followed by a slow, sustained time-release of drugremaining in the hydrogel lining. Preferred hydrogel-drug combinationsare those that employ a binding of the drug, such as electrostaticbinding, e.g., by using a poly(acrylic acid) hydrogel in combinationwith an ammonium cation and heparin or urokinase. -In this case, thecoating continues to release drug after expansion of the stent andremoval of the balloon catheter. The stent may be a balloon-expansiblestent as described above or a self-expanding stent, e.g., of the typeformed with superelastic materials such as Nitinol.

EXAMPLE 2 Lining of an Intravascular Stent with a Hydrogelpost-deployment of the stent into a body

[0035] A stent 50 that has been previously been deployed, i.e., expandedand lodged in the vessel 54, may be lined by introducing a ballooncatheter 51 with a hydrogel coating 52 into the body lumen any timeafter stent deployment as shown in FIG. 4. The balloon portion of thecatheter is positioned such that the hydrogel-coated portion isproximate to the inner surfaces of the stent, and the balloon isinflated so that the hydrogel coating of the balloon contacts the innersurface of the stent and compresses the hydrogel against the stentthereby releasing the hydrogel from the balloon to the stent creating alining therein. Alternatively, an infusion balloon or channel balloonmay be used to administer a hydrogel lining to a previously-deployedstent as described below.

[0036] A Palmaz-Schatz stent was expanded in a model blood vessel, e.g.,tygon tubing, as shown in FIG. 5. A polyethylene angioplasty ballooncatheter was coated with a hydrogel (approximately 10% solution ofpoly(acrylic acid); e.g., 10-20% poly(acrylic acid)). To line thepreviously-deployed Palmaz-Schatz stent, the catheter was inserted intothe model blood vessel and advanced to the area of the expanded stent,positioning the balloon portion proximate to the inner surfaces of thestent. The balloon was then inflated to contact the expanded stent. Upondeflation of the balloon, the coating was substantially transferred tothe inner surfaces of the stent, thereby filling the interstices of thestent and lining the stent with poly(acrylic acid) (see FIG. 6).

EXAMPLE 3 Lining an Intravascular Stent by Applying the Hydrogel to theInner Surfaces of the Stent from a Infusion Balloon or Channel Balloon

[0037] Delivery of a hydrogel stent lining with or without an associateddrug to the inner surfaces of the stent may be accomplished via adelivery port in a catheter or via a channeled balloon. A ballooncatheter having pores or channels, e.g., a channel balloon, is discussedin Wang, U.S. Pat. No. 5,254,089, and Barry, U.S. Pat. No. 5,439,466,both of which are hereby incorporated by reference. Infusion catheterswhich have one or more ports or openings adjacent to a balloon portion,i.e., upstream of the balloon portion relative to the direction of bloodflow, can also be used to deliver the hydrogel to the inner surfaces ofthe stent. In this case, the hydrogel would be administered from portsor channels in close proximity to the inner surfaces of the stent tocreate a lining within the stent.

[0038] Inflating the balloon portion of the catheter to contact thevessel wall substantially occludes the vessel and inhibits blood flow.Inflation of the balloon also urges the stent from its compactedcondition to its expanded, operative condition spanning the occludedregion of the vessel and contacting the adjacent normal vessel wall. Thehydrogel may then be delivered to the inner surfaces of the stent viaaperatures or channels of a channeled balloon over which the stent ismounted to form a stent lining. An apparatus for delivering albumin to astent is described in U.S. Pat. No. 5,439,446, hereby incorporated byreference. In the case of a pre-existing stent, an infusion or channelballoon is introduced into the vessel, positioned so that the ports orchannels are in close proximity to the inner surfaces of the stent, andthe hydrogel administered through the ports or channels to contact thosesurfaces to create a lining within the stent. In either case, thehydrogel exits the balloon through the apertures of the balloon surfaceto contact the stent proximate thereto.

EXAMPLE 4 Hydrogel Crosslinking

[0039] To minimize loss of the hydrogel coating from the balloon portionof the catheter during deployment, a hydrogel polymer may becrosslinked. The crosslinking may be physical or chemical. For example,the crosslinks may be in the form of covalent or ionic bonds or weakerinteractions such as van der Waals forces and hydrogen bonds.

[0040] For example, a hydrogel polymer such as agarose or gelatin can becrosslinked via hydrogen bonds. Such hydrogels are preferably stablycrosslinked at 37° C. When a balloon is positioned at the site at whichthe hydrogel is to be released, heat is applied to the hydrogel todisrupt the hydrogen bonds. The “melted” hydrogel is then released tothe inner surfaces of a stent or the wall of a lumen upon inflation ofthe balloon and concomitant compression of the hydrogel against thestent or tissue. Application of heat to the hydrogel is thendiscontinued, the balloon is deflated, and the catheter is withdrawnfrom the site. The deposited hydrogel returns to body temperature, i.e.,approximately 37° C., allowing the hydrogen bonds to reform. Anyphysiologically-compatible hydrogel with a melting temperature ofgreater than 37° C. can be used in this manner. Agarose is typicallyused at a concentration of 0.5-5%, preferably at a concentration ofabout 1-2%.

[0041] An alginate hydrogel polymer is reversibly crosslinked in thepresence of divalent cations. For example, an alginate hydrogel can becrosslinked by contacting it with a solution of calcium gluconate. Thecrosslinking is reversed by contacting the hydrogel with a chelatingagent. A channel balloon can be coated with a crosslinked hydrogel,delivered to a desired site, an agent which disrupts the crosslinkingbonds dispensed through the channels of the balloon to contact thehydrogel, and the hydrogel released from the balloon. The hydrogel canbe crosslinked again after deposition onto the inner surfaces of a stentor a lumen wall, e.g., by dispensing a solution of divalent cationsthrough the channels of the balloon to contact the deposited hydrogel.

EXAMPLE 5 Stent Lining for Treating Aneurisms

[0042] Stents have been used to treat vascular aneurisms such as aorticor intercranial aneurisms. Such stents are typically impermeable, e.g.,they may be covered with woven dacron, to prevent blood from enteringand pooling in the aneurism. A problem with using an impermeable stentto treat vascular aneurisms is that blood flow to both affected andhealthy regions of a blood vessel are blocked by the stent. In manycases, intercranial aneurisms occur at a point of bifurcation of healthyvessels. In such a case, it is desirable to block blood flow to theaneurism but undesirable to block blood flow to or from healthycollateral vessels.

[0043] An open mesh stent, e.g., a branched stent (Nitinol DevelopmentCorporation), is deployed to the area of an aneurism. Since an open meshstent changes the pattern of blood flow in the vessel in which it isdeployed, blood may no longer enter and pool in the aneurism, obviatingthe need for further treatment. However, if the stent alone is not aneffective treatment, a second procedure to line the stent to render itimpermeable can be performed. An advantage of the stent lining methoddescribed herein is that selected areas of the stent, e.g., an area nearor adjacent to an aneurism, may be lined, leaving other areas, e.g.,areas of healthy tissue, areas of bifurcation, or areas in which healthycollateral vessels enter or exit, unlined. For example, a hydrogelpolymer which is insoluble in blood can be delivered to the innersurface of a stent at the site of an aneurism using a balloon catheter.The polymer, e.g., poly (acrylic acid), can be delivered as a coating ona balloon portion of a catheter and released to the inner surface of astent near or adjacent to an affected portion of the vessel by expansionof the balloon. Alternatively, a dacron patch may be adhered toa-polymer coating and delivered to the aneurism site for release to theinner surface of the stent at the aneurism site. The dacron patch itselfmay be coated with a polymer to facilitate its attachment to the innersurface of the stent. Thus, an open mesh stent is rendered impermeableonly in the area of the polymer lining or dacron patch but remainspermeable in unlined areas. As a result, the flow of blood in linedportions of the stent is directed down the length of the stent ratherthan through the interstices of the stent. In unlined regions of thestent, blood can flow through the interstices of the stent, e.g., to orfrom collateral vessels.

[0044] Other embodiments are within the following claims.

What is claimed is:
 1. A catheter assembly for delivering an expansiblestent to a body lumen and lining said stent with a hydrogel, comprising(a) a catheter comprising a balloon at least a portion of which iscoated with a hydrogel; and (b) said stent mounted on said balloon in acontracted condition for passage with said catheter into said body lumenwhereby expansion of said balloon lodges said stent in said body lumenwith a hydrogel coated on an inner surface of the stent.
 2. The assemblyof claim-1, wherein said hydrogel is crosslinked.
 3. The assembly ofclaim 1, wherein said hydrogel is selected from the group consisting ofa polyacid, cellulosic polymer, collagen, gelatin, albumin, alginate,poly 2-hydroxyethyl methyl acrylate (HEMA), polyvinylpyrrolidone, maleicanhydride polymer, polyamide, polyacrylamide, polyvinyl alcohol,polyethylene glycol, and polyethylene oxide, and polysaccharide.
 4. Theassembly of claim 1, wherein said hydrogel is poly(acrylic acid).
 5. Theassembly of claim 4, wherein said poly(acrylic acid) is crosslinked. 6.The assembly of claim 1, wherein said hydrogel is hyaluronic acid. 7.The assembly of claim 6, wherein said hyaluronic acid is crosslinked. 8.The assembly of claim 1, wherein said hydrogel comprises a therapeuticagent.
 9. The assembly of claim 8, wherein said therapeutic agent is ananti-thrombogenic agent.
 10. The assembly of claim 9, wherein saidantithrombogenic agent is selected from the group consisting of heparin,PPACK, enoxaprin, aspirin, and hirudin.
 11. The assembly of claim 8,wherein said therapeutic agent inhibits platelet deposition.
 12. Theassembly of claim 8, wherein said therapeutic agent is a thrombolyticagent.
 13. The assembly of claim 12, wherein said thrombolytic agent isselected from the group consisting of urokinase, streptokinase, andtissue plasminogen activator.
 14. A catheter assembly for delivering anexpansible stent to a body lumen and lining said stent with a hydrogel,comprising (a) a catheter comprising a balloon and a delivery port foradministering a hydrogel to an inner surface of said stent; and (b) saidstent mounted on said balloon, said stent being in a contractedcondition for passage with said catheter into said body lumen wherebyexpansion of said balloon lodges said stent in said body lumen, whereinsaid hydrogel is administered through said delivery port and depositedon an inner surface of said stent as a lining.
 15. The assembly of claim14, wherein said balloon comprises a first layer and a second outeraperatured layer overlying said delivery port, wherein said hydrogel isadministered through said outer aperatured layer.
 16. The assembly ofclaim 14, wherein said hydrogel comprises a therapeutic agent.
 17. Amethod for lining a stent, comprising (a) providing a catheter assemblycomprising a balloon at least a portion of which is coated with ahydrogel, wherein an expansible stent is mounted on said balloon in acontracted condition, (b) introducing said assembly into a body lumen,and (c) inflating said balloon to lodge said stent in said body lumenand to release said hydrogel from said coated portion to an innersurface of said stent as a lining.
 18. The method of claim 17, whereinsaid body lumen is a blood vessel.
 19. The method of claim 18, whereinsaid vessel is an occluded artery.
 20. The method of claim 17, whereinsaid hydrogel comprises a therapeutic agent.
 21. A method of lining astent positioned in a body lumen, comprising: (a) providing a cathetercomprising a balloon at least a portion of which is coated with ahydrogel, (b) introducing said catheter into said body lumen, (c)advancing said catheter in said body lumen until said coated portion ispositioned proximate to an inner surface of said stent; and (d)inflating said balloon to release said hydrogel from said coated portionto said inner surface of said stent as a lining.
 22. The method of claim21, further comprising crosslinking said hydrogel.
 23. The method ofclaim 21, wherein said catheter further comprises a sheath over saidhydrogel.
 24. The method of claim 23, comprising removing said sheathprior to inflating said balloon.
 25. A method of lining a stentpositioned in a body lumen, comprising (a) providing a cathetercomprising a balloon and a delivery port, wherein said balloon comprisesa first layer and a second outer aperatured layer overlying saiddelivery port, (b) introducing said catheter into said body lumen, (c)advancing said catheter in said body lumen until said outer aperaturedlayer is positioned proximate to an inner surface of said stent; (d)delivering a hydrogel into a space between said first layer and saidsecond outer aperatured layer, and (d) inflating said balloon to presssaid hydrogel through said outer aperatured layer, wherein said hydrogelis deposited on said inner surface of said stent as a lining.
 26. Themethod of claim 25, further comprising crosslinking said hydrogel.
 27. Amethod of selectively lining a permeable stent to treat an aneurism,comprising (a) providing a catheter comprising a balloon at least aportion of which is coated with a hydrogel, (b) introducing saidcatheter into an aneurismal blood vessel comprising said permeable stentin the region of said aneurism, (c) advancing said catheter in saidvessel until said coated portion is positioned proximate to saidaneurism; and (d) inflating said balloon to release said hydrogel fromsaid coated portion to an inner surface of said stent proximate to saidaneurism to selectively line said stent, wherein said hydrogel renderssaid surface impermeable thereby reducing blood flow into said aneurism.